The glycosylphosphatidylinositol-anchored lymphocyte antigen CDw52 is associated with the epididymal maturation of human spermatozoa

The CAMPATH-1 (CDw52) antigen is a small glycosylphosphatidylinositol (GPI) anchored glycoprotein with a mature peptide comprising only 12 amino acids. It is abundantly expressed on human lymphocytes and is an unusually good target for complement-mediated cell lysis. The immunosuppressive and lymphocyte-depleting effects of CAMPATH-1 antibodies are being tested in a variety of diseases. Here we show that the antigen is also expressed at a high level in the male reproductive system, being found in the epididymis, seminal vesicle, seminal plasma and on the surface of mature (but not testicular) spermatozoa. Its possible transfer from epithelial cells in the epididymis to maturing sperm may represent a novel method of acquisition of cell surface antigens. In the presence of human complement, CAMPATH-1 antibodies inhibited the motility of washed sperm. However, seminal plasma blocks antibody binding and can protect sperm from this cytotoxic effect.